This invention relates generally to implantable medical devices, and more particularly, to an implantable adjustable fixation device having reduced infection.
Implantable medical devices comprise one or more components which are temporarily or permanently implanted in a patient or recipient. Examples of such medical devices are implantable hearing prostheses which address hearing loss in the recipient. There are generally two types of hearing loss, conductive and sensorineural. Sensorineural hearing loss is due to the absence or destruction of the cochlear hair cells which transduce sound into nerve impulses. Various hearing prostheses have been developed to provide individuals suffering from sensorineural hearing loss with the ability to perceive sound. For example, cochlear implants have an electrode assembly that is implanted in the cochlea. In operation, electrical stimuli are delivered to the auditory nerve via the electrode assembly, thereby bypassing the inoperative hair cells to cause a hearing percept.
Conductive hearing loss occurs when the natural mechanical pathways that provide sound in the form of mechanical energy to cochlea are impeded, for example, by damage to the ossicular chain or ear canal. For a variety of reasons, individuals having conductive hearing loss are typically not candidates for a cochlear implant. Such individuals typically receive an acoustic hearing aid. Hearing aids rely on principles of air conduction to transmit acoustic signals to the cochlea. In particular, hearing aids amplify received sound and transmit the amplified sound into the ear canal. This amplified sound reaches the cochlea in the form of mechanical energy, causing motion of the perilymph and stimulation of the auditory nerve.
Unfortunately, not all individuals suffering from conductive hearing loss are able to derive suitable benefit from hearing aids. For example, some individuals are prone to chronic inflammation or infection of the ear canal. Other individuals have malformed or absent outer ear and/or ear canals resulting from a birth defect, or as a result of medical conditions such as Treacher Collins syndrome or Microtia.
For these and other individuals, another type of hearing prosthesis has been developed in recent years. This hearing prosthesis, commonly referred to as a middle ear implant, converts received sound into a mechanical force that is applied to the ossicular chain or directly to the cochlea via an actuator implanted in or adjacent to the middle ear cavity.